Non-selective cation channels formed by Transient Receptor Potential Canonical (TRPC) proteins are known to be activated downstream from phospholipase C (PLC) signaling. However, the mechanism by which the PLC pathway activates TRPC4/C5 remains unclear. We found that coincident stimulation of Gi/o proteins and PLCδ1 (but not Gq/11-PLCβ) is necessary and sufficient for TRPC4 activation in HEK293 cells expressing TRPC4. While the currents were dependent on intracellular Ca2+ and phosphatidylinositol 4,5-bisphosphate (PIP2), both Ca2+ and PIP2 also exhibited inhibitory effects on the channel. In the brain, TRPC4 plays critical roles in the generation and maintenance of plateau potential in lateral septal neurons and dendritic branching of hippocampal neurons. Both processes require co-incidence stimulation of Gi/o and PLC pathways. Therefore, TRPC4 is a co-incident detector of Gi/o and PLC signaling, serving important regulatory function in brain and other body systems.